Apparatus for controlling magnetic chucks.



0. s. WALKER. v APPARATUS FOR CONTROLLING MAGNETIC CHUCKS.

APPLICATION FILED MAR-1% I914- Pate nfed Apr. 25, 1916.

Mfnessesf Zp.

,[zovney UNITED STATES PATENT OFFICE.

OAKLEY S. WALKER, OF WORCESTER, MASSACHUSETTS, ASSIGNOR TO 0. S. WALKER ('30., OF WORCESTER, MASSACHUSETTS. A CORPORATION OF MASSACHUSETTS.

Specification of Letters Patent.

Patented Apr. 25, 1916.

Application filed March 14, 1914. Serial No. 824,781.

To (11/ 101mm it1m1 1 c012ccrn:

lie it known that I. OAKLEY S. \VALKER, a citizen of the United States. residing at \Yorcester, in the county of "orcester and (ommonwcalth of Massachusetts. have invented a new and useful Improvement in Apparatus for-Controlling Magneticthucks, of which the following, taken in connection with the accompanying drawings. is a specification.

The present invention relates to apparatus adapted to control the flow of electric current through the magnetizing coil of coils of a magnetic chuck, and. broadly considered. involves the provision of means, comprising a suitable switch. adapted in one of its operative positions, to connect said coil or coils with a source of electrical supply in order to energize saidchuck. and furthermore. means. brought-into operation by the movement of said switch, to disconnect the coil or coils from the source of electrical supply, for passing a current in the reverse direction momentarily through said coil or coils. in order to completely dcenergize the chuck by ridding its magnets of residual magnetism. whereby to facilitate easy removal of the work held by said chuck. The above results are attainable. by the construction and arrangement of parts hereinafter set forth. and fully illustrated in the accompanying drawings. in which- Figure 1 is a diagrammatic view of apparatus comprising a preferred embodiment of my invention. the same being shown in connection with a magnetic chuck. Fig. 2 is a side view of the switch shown in Fig. 1.

Like reference characters are used to des ignate like parts in the different views.

Referring to the drawings. there is shown, at 1 a magnetic chuck provided with the magnetizing coil or coils 2. The form of the. chuck employed. and the arrangement and disposition of the coil or coils therein, form no parts of the present invention. the showing of the same in the drawings being merely illustrative. For the purposes of my invention, any form of chuck and any type of magnetizing coil may be employed.

The switch employed to control the flow of current to the coil 2 may take the form of a two pole knife switch, shown in plan view in Figsl and in side elevation in Fig. The operative parts thereof are mounted on a base 3 of suitable noirconducting material.

A pair of oppositely disposed metallic posts 1 and 5, carried by said base. are provided with suitable terminals for the connection of wires thereto. Said posts, furthermore. serve as pivotal supports for the parallel movable blades (3 and 7 respectively, of the switch, which are secured together, to oscillate in unison, by means of a pair of spacing sleeves 8 and of suitable insulating material. The latter are transversely aperturcd to receive a metallic bar 10. extending between and parallel to thcblades (3 aml T and beyond the ends thereof. At one end the bar 10 is provided with an insulating handle 11, which is employed for rocking the blades (3 and 7 about their pivotal sup ports.

The base 3 carries at one end a pair of bifurcated contacts 12 and 13, adapted to receive between their jaws the free ends of blades (5 and T. in order to connect the same to the leads 11 and 15 of the electrical supply, which are respectively connected to suitable terminals carried by said contacts 1:2 and 13. The terminal of post 1 is con nected by wire 16 with one terminal of coil a wire 17 connects the terminal of post 5 with one terminal of the primary winding 18 of an induction coil. and a wire 19 connects the other terminal of said winding 18 with the remaining terminal of coil 2. hen the switch is thrown into the position shown in Fig. 2, with the blades (3 and! in contact with their corresponding contacts 12 and 13, an electrical circuit including the coil 2 and winding 18 connected in series. is thereby completed. the course of the current therethrough being indicated by the full line arrows in Fig. 1. In this position of the switch the coil 2 constitutes the energizing means for suitably arranged magnets, which firmly retain and support the work to be operated upon. in the usual manner common to magnetic chucks. 'ithin the primary winding 18 is disposed the secondary winding 20 of said induction coil. which is provided centrally with a suitable iron core, not shown, such as is commonly employed in induction coils. ()ne terminal of winding 20 is connected by wire. 22 t0 the wire 19; the other terminal of winding 20 is connected by wire with one contact 25 of a pair of spaced contacts 24 and 2-). carried on base 3 at the opposite end thereof from the contacts 1'2 and 13. The contact :21 is connected by wire 26 to the wire 16, leading to coil 2. The contacts 24 and 25 consist of suitable metallic members, normally spaced apart and unconnected, but adapted to be connected together or bridged across by the adjacent end of the bar-10. which passes between and into contact with each of them when the free ends of the blades 6 and '7 are rocked upwardly to disconnect the coil from the source of electrical supply. The contact of bar 10 with the pair of contacts 2% and completes an electrical circuit hich includes the secondary winding 20 and the chuck coil 2, connected in series.

The parts of the switch are so proportioned that in the operation thereof to disconnect the chuck from the source of electrical supply. the bar 10 connects the contacts 24 and 25 immediately after the blades 6 and 7 .have passed out of contact with the contacts 12 and 13, respectively. Consequently, the magnetic lines of force constituting the field which has been built up by the passage of current through primary winding 18 do not dissipate upon the disconnection of said winding from the electrical supply, but are utilized to induce a current through the secondary winding 20 and its circui formed as above described. The winding 20 is so arranged with relation to the winding 18, and so connected to the coil 2, that the current in the induction circuit flows, as indicated by the broken line arrows, in the opposite direction to the magnetizing current of the chuck. The duration of the induced current is but momentary, owing to the fact that there is no current flowing through the primary winding 18 to maintain the field about the same. However, its passage through the coil 2 etfectually rids the chuck magnets of their residual magnetism, permitting the ready removal of the work from the chuck. It will be apparent, furthermore, that the movable member of the switch can be left in its above described demagnetizing position until it is again desired to energize the chuck for the purpose of holding work.

I claim- 1. The combination with an electric circuit including a coil, of means,

brought into operation by the breaking of said circuit, for directing an induced current in reverse direction through said coil.

2. The combination, with the prin'iary and secondary windings of an induction coil, of a magnetic chuck having a magnetizing coil, a switch for normally closing an electric circuit including said primary winding and said magnetizing coil, and means operate by the opening of said switch for closing a circuit including said secondary winding and said magnetizing coil.

3. The combination with an electric circuit including a coil and the primary winding of an induction coil, of means brought into operation by the breaking of said circuit for inducing a current in reverse direction through said coil.

4. The combination with an electric circuit including the primary winding'of an induction coil, of means brought into operation by the breaking of said circuit for making a second circuit including the secondary winding of said induction coil.

5. The combination with the magnetizing coil of a magnetic chuck, of a switch for connecting said coil in an electric circuit. and means, brought into ope -ation by the operation of said switch to disconnect said coil from the source of electrical supply, for inducing a current in reverse direction through said coil.

6. The combination with an electric circuit including a coil and the primary winding of an induction coil, of a switch for making and breaking said circuit, said switch adapted upon being operated to break said circuit, to make a second circuit including said coil and the secondary winding of said induct-ion coil. I

7. An electrical switch, comprising a movable member having a pair of blades and a bar, contacts for said blades at one end of the movement of said movable member, and a pair of contacts adapted to be connected by said bar at the other end of the movement of said movable member.

OAKLEY S. \VALKER.

Witnesses:

PENELOPE CoMBERBAoH, NELLIE WHALEN. 

